This circuit was obtained in an American documentation from the 80's. The transistors can be equivalent to those indicated and the crystal can reach a few tens of megahertz.
The clock circuit shown in the figure is suggested by Murata and is based on a ceramic resonator of the...
The operational amplifier of this configuration from the 70s is the 741 in its Motorola version from...
This circuit was found in the September 1971 Radio Electronics magazine. The buzzer can be...